The Way Paleontologists Identify Dinosaurs and Their Species

With the help of technology and breakthroughs in the thought process of the evolution of dinosaurs, paleontologists have been able to pretty accurately depict what these creatures would have actually looked and acted like, even pinning them down to a specific color. As discussed in class and further explained in the Teded video shown in class, dinosaur fossils with imprints of feathers contain hollow nanostructures called melanosomes that can be detected under a powerful microscope. These leave behind decayed minerals that are consistent with dye-pigments such as melanin and carotenoids. From these findings, paleontologists are able to accurately predict the pigmentation of an array of dinosaurs. But even more so than that, paleontologists have created a framework for determining what makes a dinosaur, a dinosaur. The resounding answers and conclusions for specific identification lie in the evolutionary phylogenetic tree.

There are general understandings and a few tale-tell signs that paleontologists use in determining whether a fossil is one that belongs to a dinosaur or one that belongs to other creatures, such as amphibians. These traits have changed drastically over time, but the one that maintains constant throughout the archeological discipline is the way the hip bone is structured. According to California Berkely’s Dinosauria morphology page, it states that “reduced fourth and fifth digits on the hand; foot reduced to three main toes; three or more vertebrae composing the sacrum (region of the vertebral column which attaches to the pelvis); and an open hip socket” are all considered to be derivative features that all dinosaurs share. The very first creatures possessed these traits and passed them down to their ancestors as can be seen in their well-documented phylogenetic tree. A more detailed analysis of the hip bone has differentiated dinosaurs into two more broad groups, saurischians, and ornithischians. These groups are used to distinguish between “lizard-hipped” and “bird-hipped” respectively. The construction of the hip in this fashion indicated that dinosaurs necessarily had an erect like posture, meaning their hind legs were located directly beneath their body and allowing us to better understand their movement.

Various discoveries in dinosaur fossils, primarily throughout mainland China, sparked a paradigm shift in the way paleontologists interpreted the physical make-up and appearance of dinosaurs. On numerous occasions, dinosaur fossil beds indicated that featherlike bristles very likely covered the bodies of therapods, even if they couldn’t necessarily fly. The actual, practical importance of feathers from an evolutionary standpoint is up for debate, especially for dinosaurs such as the T. Rex. Nevertheless, it gives insight into how birds have a phylogenetic relationship with dinosaurs. Those previous discoveries helped pioneer this new mode of thinking which lead to further examination of dinosaur bones. As described in a class lecture by Dr. Fox, and supported in Stephen Bodio’s article, if examined closely you will see indentations in the bone structure where feathers would have attached and anchored into the bones of theropods. This allowed paleontologists to confirm that dinosaurs probably had feathers even though the fossil deposits don't indicate feathers specifically. Feathers are made of the protein--keratin-- that is easily broken down, often eaten, and ultimately difficult to preserve over millenniums. This is why the majority of deposits and early thought did not initially convey the evolutionary link between birds and dinosaurs.

When it comes to identifying species based solely upon fossil records, there are several obstacles that prohibit a clear cut answer. A major premise underlying the identification of speciation is the ability to reproduce offspring. Paleontologists struggle with the concept of species because of the substantial time period differences in fossil dating. It's difficult to imagine, much less provide quantitative evidence that species were mating across such vast time differences. The biological species concept maintains that interbreeding populations reproduce in isolation from other species. From purely fossil records, it’s difficult to provide a finite answer. Because much of what is known about dinosaur variety relies on the phylogenetic evolution of a multitude of creatures, paleontologist struggle to pinpoint related species regardless of how similar their traits appear.